#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>

int main()
{
	int m, n;
	double x, s;
	scanf("%d %d", &m, &n);
	x = m - 28 * n;
	s = x / m * 100.0;
	printf("%.2lf%%\n", s);
	return 0;
}
//1047